Over the years, a variety of types of waveform generators have been developed. One type of waveform generator is configured to generate a waveform in which the frequency, phase and/or amplitude changes from mono-cycle to mono-cycle, or even within a single mono-cycle. Existing waveform generators of this type have been implemented using analog circuitry, where phase and/or amplitude changes are often made using microwave phase shifters and attenuators, and frequency changes are often made using a signal generator having a degree of capability for frequency variation. While analog circuits of this type have been generally adequate for their intended purposes, they have not been satisfactory in all respects.
In this regard, an analog waveform generator of this type is relatively complex and expensive, and is usually hardwired to produce a particular waveform. Consequently, the typical analog generator has little or no flexibility to permit variation of the waveform that it generates. When an analog waveform generator of this type is constructed in mass quantities, there will tend to be operational variations from unit to unit, due to analog considerations such as mismatch and drift of radio-frequency (RF) components within the analog circuitry. In addition, even for a single unit, accurate and dependable operation is difficult to obtain across all desired operating conditions, including temperature variations, due to factors such as the mismatch and drift of the RF components.